CN102863339A - Method for synthesizing methylethyl carbonate by ester exchange of dimethyl carbonate and diethyl carbonate - Google Patents

Abstract

The invention relates to a method for synthesizing methylethyl carbonate by ester exchange of dimethyl carbonate and diethyl carbonate, which is implemented by carrying out synthetic reaction of methylethyl carbonate on raw materials dimethyl carbonate and diethyl carbonate by using an imidazole ionic liquid as a catalyst at certain reaction temperature under ordinary pressure for some reaction time. The catalyst consumption is only 0.2-2 wt% of the dimethyl carbonate; the ionic liquid catalyst has high catalytic activity in the reaction process, the maximum yield of methylethyl carbonate is up to 62.31%, and the selectivity is 100%; and the catalyst can be recycled for cyclic utilization after being subjected to simple treatment after reaction, has the advantages of long service life and no pollution, and greatly lowers the preparation cost of methylethyl carbonate.

Description

A method for synthesizing ethyl methyl carbonate by transesterification of dimethyl carbonate and diethyl carbonate

technical field

The present invention relates to a kind of synthetic method of ethyl methyl carbonate, particularly a kind of method that adopts ionic liquid to synthesize ethyl methyl carbonate as catalyst.

Background technique

With the rapid development of lithium-ion batteries, the requirements for battery safety and service life are becoming more and more stringent, which brings challenges to the technological innovation of battery electrolytes. At present, the quality of domestically synthesized electrolyte solvents cannot meet the use standards, so electrolyte solvents are generally imported from abroad. In recent years, it has been found that ethyl methyl carbonate can be used as a good electrolyte for lithium-ion batteries. Ethyl methyl carbonate is a A wide range of asymmetric carbonate compounds, mainly used as solvents and intermediates in organic synthesis, when used as electrolyte solvents for lithium-ion batteries, due to its low viscosity, high dielectric constant, and strong solubility for lithium salts, it can be used very well The energy density and charge-discharge capacity of the battery can be greatly improved, the safety performance and service life of the battery can be improved, and the domestic demand for electrolyte can be alleviated to a certain extent.

At present, there are three main synthetic methods of ethyl methyl carbonate: phosgene method, carbonyl oxidation method and transesterification method. The phosgene method mainly uses phosgene to react with absolute ethanol. Because phosgene is highly toxic, the intermediate product is highly corrosive, and the by-products pollute the environment seriously, so this method has been eliminated. The carbonyl oxidation method is not yet perfect, and has disadvantages such as low selectivity, expensive catalyst, and difficult operation and control. So far, many researchers have done a lot of research on the synthesis of ethyl methyl carbonate by transesterification, but most of the work is mainly between methyl chloroformate and methanol, between dimethyl carbonate and methanol, and between dimethyl carbonate and diethyl carbonate. For the transesterification reaction between esters, the catalysts used for these three transesterification reactions are mostly basic catalysts, and each has its own advantages and disadvantages.

The reaction of dimethyl carbonate and diethyl carbonate to prepare ethyl methyl carbonate is a reversible reaction. There is no pollution in the reaction process. There is no azeotropic system in the reaction product system. Both the raw materials and products of the reaction can be used as non-water-soluble electrolytes for lithium batteries solvent. Therefore we choose this transesterification method to synthesize ethyl methyl carbonate. However, in this reaction system, it is important to select a catalyst.

US5962720 uses SmL ₂ , Li, LiOCH ₃ and CaH ₂ as reaction catalysts, but it takes three days to reach the reaction equilibrium.

JP10237026 uses titanium oxide as the active component of the catalyst, but the yield of the product ethyl methyl carbonate is extremely low.

JP200281630 uses oxides of rare metals such as lanthanum, actinium, and scandium as catalysts. Although they are very stable in the reaction, the purity of the raw materials is very high during the reaction process, and it is difficult to carry out the reaction with conventional raw materials.

Some documents (Zhen Lu Shen, Xuan Zhen Jiang, et al, Catal. Lett., 91 (2003) 63-67) reported that MgO, LaO ₃ , ZnO and CeO ₂ were used as catalysts, among which MgO had a better catalytic effect, Under normal pressure and temperature of 103°C, the yield of ethyl methyl carbonate was 44.2% in 4 hours.

There are documents (Arudra Palani, Narasiman Gokulakrishnan et al, Appl. Catal. A: Gen., 304 (2006) 152-158) reported that Al-Zn-MCM-41 is used as a catalyst for gas phase reaction, and the activity of the initial catalyst is very high. However, the stability is insufficient, and the activity drops sharply after repeated use.

CN1394847 uses SnO ₂ /Al ₂ O ₃ , Ga ₂ O ₃ /Al ₂ O ₃ , MoO ₃ /Al ₂ O ₃ , ZrO ₂ /Al ₂ O ₃ , TiO ₂ /Al ₂ O ₃ and V ₂ O ₃ /Al ₂ O ₃ and other supported catalysts are used as catalysts, and the yield of ethyl methyl carbonate is lower than 44% under the conditions of normal pressure and 50-200 ° C for 2-48 hours.

In summary, the above-mentioned catalyzers all have certain defects in the synthesis of ethyl methyl carbonate process through the transesterification of catalyzed dimethyl carbonate and diethyl carbonate.

In recent years, ionic liquids have become a research hotspot in many research fields because of their unique advantages: (1) low vapor pressure, non-volatile, non-flammable; (2) wide liquid temperature range, good conductivity and wide Potential window; (3) Strong dissolving ability; (4) Low toxicity, recyclable; (5) Adjustable acidity and alkalinity, etc. Therefore, it has been widely researched and applied in fields such as organic synthesis, catalytic applications and organic solvents. However, there is no relevant research on the use of ionic liquids for the synthesis of ethyl methyl carbonate by transesterification of dimethyl carbonate and diethyl carbonate. reports.

Contents of the invention

The technical problem to be solved in the present invention is aimed at defects such as low product yield, poor selectivity, difficult recycling of the catalyst, and high cost in the synthesis of ethyl methyl carbonate. In order to solve the above problems, the present invention provides a catalytic The method has high activity and high selectivity, and can be recovered and continued to be recycled after simple treatment after the reaction, thereby reducing the cost of synthesizing ethyl methyl carbonate.

The technical solution adopted by the present invention to solve its technical problems is:

Using dimethyl carbonate and diethyl carbonate as raw materials, using a two-necked round bottom flask as a reactor, under normal pressure, the catalyst used is 0.2%~2% of the mass of dimethyl carbonate, and the reaction temperature is 100~120°C , the molar ratio of the reaction materials dimethyl carbonate and diethyl carbonate is 1:1, and the reaction time is 12~24h. The yield of ethyl methyl carbonate can reach up to 62.31%, and the selectivity is 100%.

As a limitation to the present invention, the catalyst described in the present invention is an ionic liquid 1-R ₁ -2-R ₂ -3-R ₃ imidazolium salt, and its structural formula is as follows:

X ^- = Cl ^- , Br ^- , OH ^- , HCO ₃ ^- , BF ₄ ^- , PF ₆ ^- ;

R ₁ , R ₂ , R ₃ =C _n H _2n+1 (n=1~4)

In the present invention, the ionic liquid is used as a catalyst in the reaction system, and good effects are obtained. During the reaction process, the ionic liquid not only has high catalytic activity, the yield of ethyl methyl carbonate can reach up to 62.31%, and the selectivity is 100%, but also can be recovered and continued to be recycled after simple treatment after the reaction, with long life and no pollution. The cost of synthesizing ethyl methyl carbonate is greatly reduced.

Detailed ways

Example

The present invention will be further described with reference to the following examples, but it should be understood that these examples are for illustrative purposes only and should not be construed as limitations on the implementation of the present invention.

Example 1

Add reaction material dimethyl carbonate and diethyl carbonate in the reactor, its mol ratio is 1:1, 1-butyl-2-methyl-3-ethylimidazolium bromide is as catalyzer, and used catalyst amount is The reactant is 1% of the mass of diethyl carbonate, the reaction temperature is 120°C, and the reaction time is 24h. Under these reaction conditions, the yield of ethyl methyl carbonate is 57.41%, and the selectivity is 100%.

Example 2

Add reaction material dimethyl carbonate and diethyl carbonate in the reactor, its mol ratio is 1:1, and 1-methyl-2-butyl-3-methylimidazolium chloride is as catalyzer, and used catalyst amount is The mass of the reactant diethyl carbonate is 0.2%, the reaction temperature is 120°C, and the reaction time is 12h. Under these conditions, the yield of ethyl methyl carbonate is 37.58%, and the selectivity is 100%.

Example 3

Add reaction material dimethyl carbonate and diethyl carbonate in the reactor, its molar ratio is 1:1, 1-butyl-2-methyl-3-butylimidazolium hexafluorophosphate is used as catalyst, and the amount of catalyst used It is 2% of the mass of the reactant diethyl carbonate, the reaction temperature is 100°C, and the reaction time is 20h. Under these reaction conditions, the yield of ethyl methyl carbonate is 22.15%, and the selectivity is 100%.

Example 4

Add reaction material dimethyl carbonate and diethyl carbonate in the reactor, its mol ratio is 1:1, and 1-ethyl-2-methyl-3-butylimidazole hydroxide is as catalyst, and used catalyst amount is The mass of the reactant diethyl carbonate is 2%, the reaction temperature is 120°C, and the reaction time is 20h. Under these reaction conditions, the yield of ethyl methyl carbonate is 57.69%, and the selectivity is 100%.

Example 5

Add reaction material dimethyl carbonate and diethyl carbonate in the reactor, its mol ratio is 1:1, 1-propyl group-2-propyl group-3-methylimidazolium bicarbonate is as catalyst, and used catalyst amount is The reactant is 1% of the mass of diethyl carbonate, the reaction temperature is 120°C, and the reaction time is 24h. Under these reaction conditions, the yield of ethyl methyl carbonate is 60.37%, and the selectivity is 100%.

Example 6

Add reaction material dimethyl carbonate and diethyl carbonate in the reactor, its molar ratio is 1:1, 1-butyl-2-methyl-3-propyl imidazolium tetrafluoroborate is as catalyst, and catalyst used The amount is 2% of the mass of the reactant diethyl carbonate, the reaction temperature is 100°C, and the reaction time is 20h. Under these reaction conditions, the yield of ethyl methyl carbonate is 16.98%, and the selectivity is 100%.

Example 7

Add reaction material dimethyl carbonate and diethyl carbonate in the reactor, its mol ratio is 1:1, 1-butyl-2-ethyl-3-methylimidazolium bromide is as catalyzer, and used catalyst amount is The mass of the reactant diethyl carbonate is 2%, the reaction temperature is 120°C, and the reaction time is 24h. Under these reaction conditions, the yield of ethyl methyl carbonate can reach up to 62.31%, and the selectivity can reach 100%.

The recycling of embodiment 8 catalyst:

Put the reaction product and catalyst in Example 7 into a rotary evaporator for rotary evaporation. The rotary evaporation conditions: 60°C, 10 ^-1 Pa. After the rotary evaporation, a small amount of yellow viscous liquid remaining in the flask is the catalyst 1-butyl Base-2-ethyl-3-methylimidazolium bromide. According to the condition of embodiment 7, this catalyst is continuously carried out 3 evaluation tests again, as shown in reaction result table 1:

Table 1 Recycling of Catalysts

Cycles Ethyl methyl carbonate selectivity (%) Yield of ethyl methyl carbonate (%) 1 100 62.31 2 100 62.47 3 100 61.92

As can be seen from Table 1, after the catalyst is recycled three times, the selectivity and yield of ethyl methyl carbonate are basically stable, which shows that the catalyst can be reused without reducing its catalytic activity, and has a good effect.

Inspired by the above-mentioned ideal embodiment according to the present invention, through the above-mentioned description content, relevant workers can make various changes and modifications within the scope of not departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, but must be determined according to the scope of the claims.

Claims (4)

1. the method for a methylcarbonate and diethyl carbonate transesterify Catalysts of Preparing Methyl Ethyl Carbonate, it is characterized in that the method is under normal pressure, take methylcarbonate and diethyl carbonate as raw material, take ionic liquid as catalyzer, under certain temperature of reaction and reaction times, carry out the building-up reactions of Methyl ethyl carbonate.

2. the method for Catalysts of Preparing Methyl Ethyl Carbonate according to claim 1 is characterized in that described ionic liquid is 1-R ₁-2-R ₂-3-R ₃Imidazole salts, its structural formula is as follows:

X ^-=Cl ^-，Br ^-，OH ^-，HCO ₃ ^-，BF ₄ ^-，PF ₆ ^-；

R ₁,R ₂，R ₃=C _nH _2n+1(n=1~4)。

3. the method for Catalysts of Preparing Methyl Ethyl Carbonate according to claim 1, the consumption that it is characterized in that described catalyst ion liquid is 0.2% ~ 2% of material carbon dimethyl phthalate quality.

4. the method for Catalysts of Preparing Methyl Ethyl Carbonate according to claim 1 is characterized in that the mol ratio of described reaction raw materials methylcarbonate and diethyl carbonate is 1:1, and temperature of reaction is 100 ~ 120 ℃, and the reaction times is 12 ~ 24h.